Cooking thermometer with audible alarm

ABSTRACT

A cooking thermometer having an audible alarm includes a skewer having a segment of a shape memory alloy wire disposed therein. The upper end of the shape memory allow wire is secured to a connecting rod which is operatively associated with a cam assembly. When the skewer and hence the shape memory alloy wire is heated, the shape memory alloy commences a phase transformation from martensite to austenite and contracts. The cam assembly serves to translate the up and down motion of the connecting rod into rotational motion which is transmitted through a spur gear assembly to a pivoting pointer positionable over a temperature indicia plate. A helical spring assembly is positioned on the top of the connecting rod which exerts stress on the connecting rod and shape memory alloy wire during the phase transformation to extend the temperature transformation range and improve and optimize the linearity of the transition.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of applicant'sco-pending U.S. application Ser. No. 10/218,980, filed Aug. 13, 2002,which is a continuation-in-part of U.S. application Ser. No. 09/677,712,filed Sep. 30, 2000, now U.S. Pat. No. 6,431,110, the contents of whichare hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to a temperature measuringdevice for use in cooking food, and particularly to a cookingthermometer having an audible alarm to alert the user when thetemperature of the food reaches a predetermined threshold level.

BACKGROUND OF THE INVENTION

[0003] Various food products must be cooked until the internaltemperature of the food reaches a predetermined temperature. This isespecially true with respect to meat due to health purposes and personalpreference. By achieving a certain internal temperature, the preparercan be reasonably certain that the food contains no living organismswhich are known to have an immediate effect in many consumers. Also, thepreparer can serve a dish that conforms to the personal preference ofthe consumer, i.e. rare, medium, or well-done without the need ofcutting open the food to check or attempt to rely solely on time cooked.

[0004] Conventional food thermometers incorporate a sensing probe forinsertion into the food. Thus, if a thermometer only indicatestemperature, the food preparer must diligently check the thermometer todetermine when the food has reached the desired temperature.

[0005] There exist various cooking thermometer type devices that providean indicator, such as a pop-up element or color change, which indicatewhen a threshold temperature has been reached in accordance with apredetermined measurement. However, these devices are generally notadjustable or precisely accurate. Thus, the preparer must diligentlycheck the indicator to determine when the indicator is activated.

[0006] Conventional thermometer devices used for cooking require thepreparer to carefully and diligently check the device to prevent thefood from becoming overcooked. Should the food preparer becomedistracted with other dishes, a phone call, etc. and forget to check thethermometer, reliance on conventional cooking thermometer devices mayresult in the food becoming overcooked and possibly inedible.

[0007] Existing mechanical meat thermometers typically use a bi-metalhelical spring in a skewer together with a spur gear assembly to turn atemperature indicating pointer. When heated, the bi-metal helical springexpands and the resulting rotational motion moves a pointer attached tothe end of the spring. Bi-metal helical springs of suitable size to beused in a meat thermometer provide only a minuscule amount of force,typically only to turn the pointer, but not enough to trigger a ringingmechanism.

[0008] To provide an improvement over prior art meat thermometers, thepresent invention provides a cooking thermometer having an audible alarmand a probe which incorporates a shape memory alloy segment of wire,such as Nickel Titanium (NiTi, commonly known as nitinol), instead ofthe bi-metal spring used in existing thermometers. Shape memory alloysundergo a thermoelastic phase transformation in their crystal structurewhen cooled from the stronger, high temperature form (Austenite) to theweaker, low temperature form (Martensite). This inherent phasetransformation is the basis for the unique properties of shape memoryalloys, including the shape memory effect, superelasticity, and highdamping capability.

[0009] When a shape memory alloy is in its martensitic form it is easilydeformed to a new shape. However, when the alloy is heated through itstransformation temperatures, it reverts to austenite and recovers itsprevious shape with great force. The temperature at which the alloyremembers its high temperature form when heated can be adjusted byslight changes in alloy composition, mechanical working, and heattreatment.

[0010] The shape memory alloys also show a superelastic behavior ifdeformed at a temperature which is slightly above their transformationtemperatures. This effect is caused by the stress-induced formation ofsome martensite above its normal temperature. Because it has been formedabove its normal temperature, the martensite reverts immediately toundeformed austenite as soon as the stress is removed. This processprovides a very springy “rubberlike” elasticity.

[0011] One of the properties of nitinol alloys is that they do notundergo their phase transformation at one particular temperature.Instead, the transformation begins at one temperature (known as thestart temperature, M_(S),) and is completed at another temperature(known as the finish temperature, A_(F)). Thus, the heat deformationproperties of shape memory alloys can be utilized to operate atemperature measurement device. For optimum economy of design, it wouldbe highly desirable to provide a cooking thermometer with an audiblealarm in which a shape memory alloy is simultaneously used for both ananalog temperature reading and also to provide the mechanical forcenecessary to trigger an alarm bell.

DESCRIPTION OF THE PRIOR ART

[0012] Yeung, U.S. Pat. No. 6,230,649, discloses a meat thermometer witha mechanical alarm bell which includes a shape memory alloy probe in theform of a coiled spring. A latch is mechanically coupled to the shapememory alloy spring and releases a wind-up mechanism when the probereaches a predetermined temperature. While the design of this device mayperform the intended function, the use of a shape memory alloy in theform of a coiled spring is highly undesirable from a manufacturingstandpoint. Shape memory alloys formed as coiled springs are extremelyexpensive to manufacture, and the production of a meat thermometer usingsuch a spring would not be economically feasible. Also, this device hasmany practical drawbacks. While an alarm sounds when the end point isreached, the device does not provide a continuous indication of theactual temperature which would enable one to estimate the cooking timeremaining. The Yeung device does not allow selective adjustment of theset point temperature, but rather each device is pre-set to an endtemperature so that finer adjustments for individual preferences (i.e.more rare vs. well done) is not possible. If a different type of meat isto be cooked, the shaped metal alloy and associated components must bechanged.

[0013] Other known prior art food visual thermometers include U.S. Pat.Nos. 4,059,997, 3,373,611, 5,312,188, and 1,918,258; and PCT PublishedApplication No. WO 90/11497.

[0014] U.S. Pat. No. 6,065,391 discloses an electronic chef's fork whichdisplays the degree of doneness of food. However, it is not adjustableand gives no audible signal.

[0015] U.S. Pat. No. 5,487,352 and U.S. Pat. No. 4,748,931 disclose apop-up temperature indicator. The devices have a meltable seal thatmelts at a set point causing a portion of the device to pop-up thusalerting the user that the food is done. Again, there is no audiblesignal.

[0016] U.S. Pat. No. 4,083,250 discloses a food thermometer with anaudible device. On reaching a set point cooking temperature, a valveopens enabling steam in a reservoir to activate a whistle alarm. Thisdevice does provide an audible alarm but requires filling and projects ahot steam upon activation.

[0017] U.S. Pat. No. 3,778,798 discloses a food thermometer forproducing an audible alarm, but it is a complex unit generally onlyavailable as a permanent part of an oven.

[0018] U.S. Pat. No. 4,089,222 discloses a device for telemetry of thetemperature of a mass undergoing temperature change, typically of acomestible being heated in an oven, and the like. The device includes aprobe having a cavity which receives a thermally expansive material suchas wax, a displacement member responsive to pressure developed by thetemperature expansive material, a sonic or ultra-sonic signal generator,a latch mechanism inhibiting operation of the audio signal generator anda rod mechanically interconnecting the displacement member with thelatch so that expansion of the material in the probe cavity trips thelatch mechanism to permit generation of an output signal. The devicealso includes adjustment means for variation in the relative positionsof the latch mechanism to the displaceable member whereby the triggeringtemperature for the latch mechanism can be fixedly

[0019] U.S. Pat. No. 3,830,191 is directed towards a timer for variousmeats, including poultry, to audibly indicate when a meat has beencooked to a desired extent. The container is filled with a solutionwhich creates steam, and upon escape of the steam an audible signal isproduced which indicates completion of cooking.

[0020] Thus, what is needed is a means for audibly alerting the foodpreparer when the internal temperature of the food being cooked reachesa predetermined temperature which has an economy of design notdemonstrated in the prior art.

SUMMARY OF THE INVENTION

[0021] Thus, it is an objective of the instant invention to provide acooking thermometer having an audible alarm for alerting the user whenthe temperature of a substance reaches a predetermined threshold level.

[0022] It is another objective of the instant invention to provide acooking thermometer probe which incorporates a linear segment of a shapememory alloy wire therein, whereby both an analog temperature indicationas well as the mechanical force necessary to trigger an audible tensionwound alarm assembly are provided.

[0023] It is a further objective of the instant invention to provide acooking thermometer with an audible alarm that does not require fillingwith water or an electrical connection for operation.

[0024] It is still another objective of the instant invention to providea cooking thermometer which does not require extraneous wires or cordsso that the device can be used in meats on a rotating spit.

[0025] It is yet another objective of the instant invention to provide acooking thermometer with an audible alarm that is adjustable andinexpensive.

[0026] It is a still further objective of the instant invention toprovide a cooking thermometer whose threshold temperature setting can beadjusted without removal from the substance into which it is inserted.

[0027] It is yet an additional objective of the instant invention toprovide a winding means for the audible alarm of a cooking thermometerwhich can be operated while the device remains inserted within thesubstance being monitored.

[0028] It is an additional objective of the instant invention to providesupplemental anchoring and anti-rotation means to aid in maintaining thecooking thermometer in its originally chosen position.

[0029] It is a further objective of the instant invention to provide amesh curtain attached to the device which serves to shield the devicefrom grease and other liquids during the cooking process.

[0030] It is a still further objective of the instant invention toprovide a cooking thermometer which does not require the changing ofinternal components for varied cooking tasks.

[0031] In accordance with the above objectives, in a preferredembodiment of the invention, a cooking thermometer having an audiblealarm is provided which is entirely mechanical in operation. The cookingthermometer has a generally cylindrical housing and a substantiallyhollow skewer extending coaxially from the lower surface of saidhousing. The housing assembly includes upper and lower portions whichrotate with respect to one another to wind an alarm spring. A rotatablering is circumferentially disposed between the upper and lower portions,and is linked to a set temperature needle so that the ring can bemanually rotated to select the alarm point on the indicia plate.

[0032] A short linear segment of a shape memory alloy wire, preferablynickel titanium, is disposed inside the skewer and fastened to thedistal end. The upper end of the shape memory alloy wire is secured to aconnecting rod which extends upwardly into the housing and is verticallydisplaceable within the skewer. The upper end of the connecting rod isoperatively associated with a cam assembly within the housing. When theskewer and hence the shape memory alloy wire is heated, the shape memoryalloy commences a phase transformation from martensite to austenite andcontracts, smoothly with significant force. The cam assembly serves totranslate the up and down motion of the connecting rod into rotationalmotion. This rotational motion drives a spur gear assembly which isconnected to a pivoting pointer positionable over a temperature indiciaplate. The spur gear assembly provides the appropriate gear ratio tomove the pointer through a predetermined arc for each degree change intemperature.

[0033] A spring biasing means, comprising a helical spring assemblyincluding at least one helical spring, is positioned on the top of theconnecting rod and exerts stress on the connecting rod and shape memoryalloy wire during the phase transformation. This stress extends thetemperature transformation range and improves and optimizes thelinearity of the transition. The spring assembly, which in a mostpreferred embodiment includes both an inner and an outer spring, hasparameters of length and spring constant which are configured to achievethe desired phase transformation characteristics.

[0034] Other objectives and advantages of this invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The drawings constitutea part of this specification and include exemplary embodiments of thepresent invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE FIGURES

[0035]FIG. 1 is a pictorial view of the cooking thermometer according toa preferred embodiment of the invention;

[0036]FIG. 2 is cross-sectional view of the cooking thermometer of theinvention;

[0037] FIGS. 3A-F are successive exploded illustrations of the internalconstruction of the housing of the cooking thermometer of the invention.

[0038]FIG. 4 is a side view of the device of FIG. 1 inclusive ofsupplemental anchoring and anti-rotation means;

[0039]FIG. 5 illustrates an alternative arrangement of the device ofFIG. 1 which includes a stainless steel mesh curtain to shield thedevice from grease; and

[0040]FIG. 6 illustrates the device of FIG. 6 inserted into a portion ofmeat to be cooked.

DETAILED DESCRIPTION OF THE INVENTION

[0041] It is to be understood that while a certain form of the inventionis illustrated, it is not to be limited to the specific form orarrangement of parts herein described and shown. It will be apparent tothose skilled in the art that various changes may be made withoutdeparting from the scope of the invention and the invention is not to beconsidered limited to what is shown and described in the specificationand drawings.

[0042] A pictorial view of the cooking thermometer device 10 accordingto a preferred embodiment is shown in FIG. 1. The device 10 has agenerally cylindrical housing assembly 12 and a skewer 18 extendingcoaxially from the lower surface. On the upper surface, a pivotingpointer 30 is positionable over a temperature indicia plate 40. Thehousing assembly 12 includes upper and lower portions rotatable withrespect to one another, namely rotatable bezel 14 and lower housing 16.A rotatable ring 15 is circumferentially disposed between the rotatablebezel 14 and the lower housing 16 and is linked to the set temperatureneedle 32 so that the ring 15 can be manually rotated to select thealarm point on the indicia plate 40.

[0043] The construction of the housing 12 can best be seen in thecross-sectional view of the device 10 as shown in FIG. 2. Rotation ofthe rotatable bezel 14 with respect to the lower housing 16 winds analarm spring 36 disposed in the lower housing (FIG. 2). The skewer 18 issubstantially hollow, and has a sharpened distal end 19 adapted topenetrate meat to be cooked. A short linear segment of a shape memoryalloy wire 20, preferably nickel titanium (nitinol) is disposed insidethe skewer 18 and fastened to the distal end 19. The upper end of thenitinol wire 10 is secured to a connecting rod 24 which extends upwardlyinto the housing 12 and is vertically displaceable within the skewer 18.Barrel crimps, such as barrel crimp 22, can be used to secure the endsof the nitinol wire 20 to the skewer and the connecting rodrespectively.

[0044] The upper end of the connecting rod 24 is linked to a camassembly which is operable to translate the vertical displacement of theconnecting rod 24 into rotational motion. In the preferred embodimentshown in FIG. 2, a rack gear assembly 26 is operativley associated withconnecting rod 24. A rotating cam assmebly can also be used. As shown indetail in FIG. 3D, the rack gear assembly 26 includes a verticallydisplaceable cam 27 which is linked to connecting rod 24. The cam 27 hasa linearly angled top surface which is adjacent to a rack gear 29. Therack gear 29 is movable normal to the cam 27 and has a angled endsurface complementary to the top surface of cam 27. The rack gear 29 isslidably disposed in a rack gear housing 21, and a gear spring 23 inrack gear housing 21 biases rack gear 29 against cam 27. Thus, verticalmotion of cam 27 results in horizontal translation of rack gear 29within the rack gear housing 21, which in turn drives a spur gearassembly 31 which is connected to a pivoting pointer 30. The spur gearassembly 31 provides the appropriate gear ratio to move the pointer 30through a predetermined arc for each degree change in temperature.

[0045] When the skewer 18 and hence the nitinol wire 20 is heated, thenitinol alloy commences a phase transformation from martensite toaustenite. In the preferred embodiment, the composition of the nitinolalloy is selected so that the transformation begins at approximately140° F. and is completed at approximately 185° F., representing the spanof temperatures required for cooking meat. The nitinol wire in thepreferred embodiment is “70C nitinol” alloy. The nitinol wire in thepreferred embodiment should measure approximately 2 inches in length andhave a diameter of approximately 0.008 inches. Though the device 10 asdescribed herein utilizes nitinol wire, any suitable shape memory wirealloy having the requisite phase transformation characteristics can beused.

[0046] During heating, as the phase transformation progresses frommartensite to austenite, the nitinol wire contracts, smoothly and withsignificant force. (The nitinol wire of the preferred embodiment wouldprovide sufficient force during the phase transformation to lift theequivalent of a 2 lb. object.)

[0047] One of the properties of shape memory wire alloys, e.g. nitinolwire, is that the overall temperature span of the transformation and thelinearity of the change in length versus temperature is a function ofmechanical stress applied thereto. In the preferred embodiment, one ofmore springs of the appropriate length and spring constant arepositioned to exert stress on the nitinol wire as it contracts, so thatthe stress exerted on the nitinol wire increases as the transformationprogresses at a predetermined rate. As shown in FIG. 1, a helical spring28 is coaxially positioned on the connecting rod 24. The upper end ofconnecting rod 24 includes a lip portion 25 which cooperates with therotating cam 26 to retain the spring 28 in position while allowingvertical displacement of the connecting rod 24.

[0048] The increasing stress exerted by the spring assembly 28, whichmay be formed from stainless steel, on the nitinol wire 20 as itcontracts provides additional separation of A_(F) and M_(F), the finishtemperatures of the transformations to austenite and martensiterespectively, thereby increasing the overall temperature span of thetransformation so that the desired operating temperature can beachieved. Simultaneously, the increasing stress exerted by the spring onthe nitinol wire during the phase transformation improves the linearityof the change in length versus temperature. In the preferred embodimentthe spring 28 is selected to have a free length of about 0.38″, a springconstant of about 7.0 lb/in, a solid length of about 0.096″ and a loadat solid length of about 1.7 lbs, which provides an operatingtemperature range of about 135° F. to 190° F. In the practice of theinvention, the spring 28 and shaped memory alloy element can each bespecified to encompass parameters which would permit operation in aplurality of desired temperature ranges, so the device can be used tomeasure the temperature for a variety of different substances.

[0049] The maximum recoverable strain limit for both superelastic andshape memory nitinol is approximately 6 to 8%. However, in the preferredembodiment, to increase repeatability, the strain is limited to 4%. Inthe preferred embodiment, using 2 inch length of wire, 4% strainrepresents a movement of the wire and the connecting rod of 0.080inches, which is sufficient to accomplish the desired purpose. Limitingthe strain to 4% enables the heating/cooling cycle to be accuratelyrepeated up to 100,000 times.

[0050] In a particularly preferred embodiment, the spring 28 is a springassembly comprising two springs, an inner spring as described above, andan outer spring (not shown) which has a free length of about 0.335 in.,a spring constant of about 7.3 lbs./in, a solid length of about 0.104in., and a load at solid length of about 2.3 lbs. This second or outerspring is constructed and arranged to come under no load until thenitinol wire is shortened to approximately half of its 0.080 in. travellength. Application of additional stress at the point of 50% traveldistance of the nitinol expands the range of austenite/martensitetransition and improves linearity of the temperature response. Byutilizing the second spring configuration, tuning of the device is moreeasily accomplished, since the second spring mediates optimization ofboth the austenite/martensite transition region and linearity of thetemperature response.

[0051] FIGS. 3A-F successively illustrate exploded views of theconstruction of the device 10. In FIG. 3A, rotatable bezel 14, rotatingring 15 and indicia plate 40 have been removed. It can be seen that theset point needle is integrally formed with a set point disk 42 whichincludes a tab 44 which is attached to rotating ring 15 (shown FIG. 1).The set point disk 42 includes a plurality of radially disposedapertures 45 which are configured to engage with cooperating protrusions48 in the underlying trigger disk 47 (FIG. 3B) which is fixedly attachedto the pointer 30 such that the trigger disk 47 rotates with pointer 30.As seen in FIG. 3B, the trigger disk is biased upward by a leaf spring50. The leaf spring 50 includes a first fixed end 52 and a second freeend 53. The free end 53 includes downwardly depending lip portion whichextends into a slot 55 (FIG. 4B). The apertures 45 and the protrusions48 are configured to be in engageable alignment when the pointer 30 andset point needle 32 coincide. When the pointer 30 reaches the set pointneedle 32, the protrusions are seated in the apertures, and the biasingforce of the leaf spring urges the trigger disk upward, thus releasingthe lip portion of the leaf spring from the slot 55. Referring to FIG.3D, it is seen that this motion releases a hammer and bell assembly 56which is driven by ringer spring 36 (FIG. 3E), and the alarm sounds. Thephase transformation of the nitinol wire 20 (FIG. 2) provides the forceto rotate the trigger disk 47 and pointer 30, and thus the forcenecessary to trigger the bell and hammer alarm assembly 37.

[0052] The above-described preferred embodiment is inclusive of anaudible spring-wound alarm, however in an alternative embodiment of theinvention, the alarm assembly is omitted from the device 10. For such anembodiment, the rotatable bezel 14 could be omitted, and the temperatureset point selected by rotation of the rotatable ring 15 with respect tothe housing assembly 12.

[0053] With reference to FIG. 4, a pictorial view essentially as setforth in FIG. 1 is shown inclusive of one or more additional anchorageenhancement elements which can include anchoring protrusions 402, pluralanchoring barbs 404 or combinations thereof. While these improvementsare shown in the FIG. 1 embodiment, it is understood that they are notso limited, and may be included in any of the illustrated embodiments orequivalents thereof. The protrusions 402 and barbs 404 serve to enhancethe ability of the instant thermometer device to remain in positiongiven the dynamics encountered during cooking, for example in arotisserie.

[0054]FIG. 5 illustrates an alternative embodiment of food temperaturemeasuring device 10 which includes a mesh curtain 122 which serves toprevent grease from entering the housing through the openings betweenthe rotatable bezel 14, the rotatable ring 15 and lower housing 16. Inthis embodiment, the rotatable bezel 14 includes an outwardly extendingcircumferential lip 111. A plurality of piercing implements 120 extenddownwardly from the lip 111 so as to be substantially parallel to theskewer 42. In the preferred embodiment, the piercing implements 120 havea length less than the length of skewer 18, and anchor the device inplace when the device is inserted into a food item. A mesh curtain 122formed as a tube is circumferentially attached to the lip 111, and ispreferably stainless steel mesh. A plurality of ring members 126 extendthrough said the mesh curtain 120 in alignment with the piercingimplements 120. The ring members 126 are slidably positionable on thepiercing elements 120 so that the mesh curtain 122 can be moved betweenraised and lowered positions relative to the piercing elements 120. Inuse, the device 10 is inserted into a portion of meat to be cooked untilthe piercing elements 120 are secured therein so that the somewhatcompressed mesh curtain 120 rests on the surface of the meat, as shownin FIG. 6. The lower portion of the housing assembly 12 is thuscontained within the mesh curtain 120, which advantageously preventsgrease and other materials from reaching the sides and lower surface ofthe housing assembly 12.

[0055] All patents and publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

[0056] It is to be understood that while a certain form of the inventionis illustrated, it is not to be limited to the specific form orarrangement of parts herein described and shown. It will be apparent tothose skilled in the art that various changes may be made withoutdeparting from the scope of the invention and the invention is not to beconsidered limited to what is shown and described in the specificationand drawings.

[0057] One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objectives and obtain theends and advantages mentioned, as well as those inherent therein. Theembodiments, methods, drawings, procedures and techniques describedherein are presently representative of the preferred embodiments, areintended to be exemplary and are not intended as limitations on thescope. Changes therein and other uses will occur to those skilled in theart which are encompassed within the spirit of the invention and aredefined by the scope of the appended claims. Although the invention hasbeen described in connection with specific preferred embodiments, itshould be understood that the invention as claimed should not be undulylimited to such specific embodiments. Indeed, various modifications ofthe described modes for carrying out the invention which are obvious tothose skilled in the art are intended to be within the scope of thefollowing claims.

What is claimed is:
 1. A cooking thermometer having an audible alarm,comprising: a generally cylindrical housing assembly and a substantiallyhollow skewer extending coaxially therefrom, said skewer having aproximal end contiguous to said housing assembly and a sharpened distalend; said housing assembly further including a temperature indiciaplate, a pivoting pointer movable over said indicia plate; a settemperature needle selectably manually positionable over said indiciaplate, and a tension wound spring-type audible alarm mechanism activatedby alignment of said set temperature needle and said pointer, a linearsegment of heat contractible shape memory alloy wire disposed withinsaid skewer and having a first end and a second end wherein said firstend is fastened to said distal end of said skewer, said shape memoryalloy wire being selected such that said wire begins phasetransformation at a first lower temperature M_(S) and completes phasetransformation at a second higher temperature A_(F); a connecting roddisposed within said skewer and secured to said second end of said shapememory alloy wire; said connecting rod having an upper end extendinginto said cylindrical housing assembly; a cam assembly operativelyassociated with said connecting rod wherein vertical movement of saidconnecting rod is translated into rotational motion and transmitted tosaid pointer through a gear assembly; and a spring biasing meansconstructed and arranged to exert stress on said shape memory alloy wireduring phase transformation, said spring biasing means having parameterswhich are configured to impart desired phase transformationcharacteristics to said shape memory alloy; whereby optimization of saidaustenite/martensite phase transition and linearity of temperatureresponse are obtained.
 2. The cooking thermometer of claim 1, whereinM_(S) is approximately 140° F. and A_(F) is approximately 185° F.
 3. Thecooking thermometer of claim 1, wherein said shape memory alloy isnickel titanium.
 4. The cooking thermometer of claim 1, wherein saidspring biasing means is at least one helical spring coaxially positionedon the upper end of said connecting rod, said at least one helicalspring housed between upper and lower retaining members wherein saidupper retaining member is contiguous to said connecting rod wherebycontraction of said shape memory alloy compresses said spring.
 5. Thecooking thermometer of claim 1, wherein said at least one helical springhas a spring constant of about 7.0 lb/in., a free length of about 0.38in., a solid length of about 0.096 in., and a load at solid length ofabout 1.7 lbs.
 6. The cooking thermometer of claim 5, further includinga second helical spring which does not come under load until said shapememory alloy has contracted about 50% of its travel distance, saidsecond spring having a spring constant of about 7.3 lb./in., a freelength of about 0.335 in., a solid length of about 0.104 in. and a loadat solid length of about 2.3 lbs..
 7. The cooking thermometer of claim1, wherein said housing assembly includes upper and lower portionsrotatable with respect to one another, wherein rotation of said upperportion with respect to said lower portion winds said alarm mechanism.8. The cooking thermometer of claim 7, wherein said housing assemblyfurther includes a rotatable central ring portion circumferentiallydisposed between said upper and lower portions, said central ringportion linked with said set needle to allow manual selection of a settemperature by rotation of the ring portion.
 9. The device of claim 1,wherein said housing assembly further comprises a circumferential lipextending outwardly therefrom and a plurality of radially arrangedpiercing implements depending from said circumferential lip parallel tosaid skewer; a mesh curtain formed as a tube circumferentially attachedto said lip and extending downwardly therefrom; and a plurality of ringmembers extending through said mesh curtain proximate said piercingimplements, said ring members slidably positionable on said piercingelements.
 10. The device of claim 9, wherein said mesh curtain iscomprised of stainless steel mesh.
 11. The device of claim 1, whereinthe distal end of said skewer includes a plurality of barbs extendingtherefrom adapted to retain said skewer within a food item.
 12. Acooking thermometer, comprising: a generally cylindrical housingassembly and a substantially hollow skewer extending coaxiallytherefrom, said skewer having a proximal end contiguous to said housingassembly and a sharpened distal end; said housing assembly furtherincluding a temperature indicia plate and a pivoting pointer movableover said indicia plate; a linear segment of heat contractible shapememory alloy wire disposed within said skewer and having a first end anda second end wherein said first end is fastened to said distal end ofsaid skewer, said shape memory alloy wire being selected such that saidwire begins an austenite/martensite phase transformation at a firstlower temperature MS and completes phase transformation at a secondhigher temperature AF; a connecting rod disposed in said skewer andsecured to said second end of said shape memory alloy wire; saidconnecting rod having an upper end extending into said cylindricalhousing assembly; a cam assembly operatively associated with saidconnecting rod wherein vertical movement of said connecting rod istranslated into rotational motion and transmitted to said pointerthrough a gear assembly; and a spring biasing means constructed andarranged to exert stress on said shape memory alloy wire during phasetransformation, said spring biasing means having parameters which areconfigured to impart desired phase transformation characteristics tosaid shape memory alloy; whereby optimization of saidaustenite/martensite phase transition and linearity of temperatureresponse are obtained.
 13. The cooking thermometer of claim 12, whereinMS is approximately 140° F. and AF is approximately 185° F.
 14. Thecooking thermometer of claim 12, wherein said shape memory alloy isnickel titanium.
 15. The cooking thermometer of claim 12, wherein saidspring biasing means is at least one helical spring coaxially positionedon the upper end of said connecting rod, said at least one helicalspring housed between upper and lower retaining members wherein saidupper retaining member is contiguous to said connecting rod wherebycontraction of said shape memory alloy compresses said spring.
 16. Thecooking thermometer of claim 15, wherein said helical spring has aspring constant of about 7.0 lb/in., a free length of about 0.38 in., asolid length of about 0.096 in., and a load at solid length of about 1.7lbs.
 17. The cooking thermometer of claim 16, further including a secondhelical spring which does not come under load until said shape memoryalloy has contracted about 50% of its travel distance, said secondspring having a spring constant of about 7.3 lb./in., a free length ofabout 0.335 in., a solid length of about 0.104 in. and a load at solidlength of about 2.3 lbs.
 18. The cooking thermometer of claim 12,further comprising a set temperature needle selectably manuallypositionable over said indicia plate.
 19. The cooking thermometer ofclaim 18, wherein said housing assembly further includes a rotatablecentral ring portion circumferentially disposed between said upper andlower portions, said central ring portion linked with said set needle toallow manual selection of a set temperature by rotation of the ringportion.